thardy3
TYF Newbie
So, this has been something that I've been chasing for about a week now in my '99 Tahoe 5.7. I'll start from the top.
About a week ago, jumped on the highway to leave work, got up to cruising speed, and when I tried to accelerate slightly I felt and heard it misfire. Looked down and saw the CEL come on. Had it scanned immediately and it threw a P0304 - Cylinder #4 misfire. That Saturday, took it over to a buddy's shop check plugs and wires, both were in need of swapping, so we replaced all plugs, wires, rotor, and cap. All parts were AC Delco brand. Cranked it back up and it still wasn't running quite right. My buddy has seen a similar issue before and it turned out to be the catalytic converter. So we checked temps of both while running and one was up about 250 deg hotter than the other. Did the knock test on it and it was rock solid. Cut it off and just welded straight pipe back up. Cranked it and she ran great, CEL even went away.
No issues till today. Jump back on the highway, first time since the other incident, and it acts very similar, but not as bad. Had it scanned and this time it was a P0300 code. Didn't really seem to be running bad or anything just the light being on. The really random part is that when I left work, I made a pit stop, cranked it back up and the CEL was once again gone!
Has anyone ever heard of this before, any suggestions? It's like it doesn't like to be run on the highway or something. I think she's trying to tell me something!
About a week ago, jumped on the highway to leave work, got up to cruising speed, and when I tried to accelerate slightly I felt and heard it misfire. Looked down and saw the CEL come on. Had it scanned immediately and it threw a P0304 - Cylinder #4 misfire. That Saturday, took it over to a buddy's shop check plugs and wires, both were in need of swapping, so we replaced all plugs, wires, rotor, and cap. All parts were AC Delco brand. Cranked it back up and it still wasn't running quite right. My buddy has seen a similar issue before and it turned out to be the catalytic converter. So we checked temps of both while running and one was up about 250 deg hotter than the other. Did the knock test on it and it was rock solid. Cut it off and just welded straight pipe back up. Cranked it and she ran great, CEL even went away.
No issues till today. Jump back on the highway, first time since the other incident, and it acts very similar, but not as bad. Had it scanned and this time it was a P0300 code. Didn't really seem to be running bad or anything just the light being on. The really random part is that when I left work, I made a pit stop, cranked it back up and the CEL was once again gone!
Has anyone ever heard of this before, any suggestions? It's like it doesn't like to be run on the highway or something. I think she's trying to tell me something!
